Mika Kivimaki, Professor of Epidemiology at University College London, UK, and colleagues did a systematic review and meta-analysis of published studies and unpublished individual-level data examining the effects of longer working hours on cardiovascular disease up to August 20, 2014.

Analysis of data from 17 studies involving 528,908 men and women who were followed up for an average of 7.2 years, found a 1.3 times higher risk of stroke in individuals working 55 hours or more a week compared with those working standard hours.

This association remained even after taking into account health behaviours such as smoking, alcohol consumption, and physical activity, and standard cardiovascular risk factors including high blood pressure and high cholesterol.

Importantly, the researchers found that the longer people worked, the higher their chances of a stroke.

"The pooling of all available studies on this topic allowed us to investigate the association between working hours and cardiovascular disease risk with greater precision than has previously been possible," Kivimaki said.

"Health professionals should be aware that working long hours is associated with a significantly increased risk of stroke, and perhaps also coronary heart disease," said Kivimaki.